The present invention relates to a method and to a device for estimating channel properties of a transmission channel. Specifically, it may provide compensation of attenuation or dispersion effects, caused by the respective electrical transmission channel, as a function of the assessed channel properties.
When electrical signals are transmitted via a wired or wireless transmission channel, the signals arriving at the respective receiver no longer have the same signal form as at the transmitter as a result of the physical properties of the transmission channel or transmission medium. These signal changes are a consequence of the frequency-dependent attenuation and dispersion characteristics of the transmission path. The signal quality at the receiver also decreases as the length of the transmission channel, for example a copper conductor, increases. If a critical length is exceeded, the received signal can sometimes no longer be correctly detected. A maximum range of the signal transmission is thus defined by the physical properties of the transmission signal, which will hereinafter be called the channel properties.
If the physical channel properties of the transmission channel, such as the attenuation and dispersion characteristics, in particular, are known to some extent, then, as a result of suitable measures on the receiver or transmitter side, the attenuation or dispersion effects caused by the transmission channel can be at least partially compensated, so an enlargement of the maximum range can be achieved due to this compensation. The quality of the compensation depends on how precisely the channel properties of the transmission channel are known. The more detailed the knowledge of the channel properties is, the better potential channel interference can be compensated. It is extremely important for a practical embodiment that the expenditure necessary when determining the channel properties and during subsequent compensation is still economically viable.
The running time and attenuation compensation of electrical transmission channels is a method that has been known and practiced for many decades, wherein different approaches have been or are used. It is therefore known, for example, to manually measure the transmission channel and then individually adjust compensation elements at the receiver or transmitter side. This approach is advantageous to the extent that very precise compensation is possible, but each transmission channel has to be individually adjusted so the expenditure is extraordinarily high. In accordance with a further approach, it is also known to select, from a set of predetermined standard parameters, a respectively suitable set of parameters for conduction compensation. In other words, compensation requires only low expenditure, although only incomplete adaptation between the sets of parameters available and the transmission channel is possible. It is also known to use digital signal processing methods for compensation, the received stream of data being analysed in the frequency range in order to be able to make conclusions about the channel properties, i.e. the physical transmission parameters of the transmission channel, from the observation of the energy distribution in the frequency range, for example. This procedure is connected with the advantage that it is very flexible and allows an adaptive compensation of potential attenuation and dispersion effects. A problem with this procedure is, however, that the transmission parameters of the transmission channel can only be indirectly assessed using heuristic methods.
The above-described approaches solve the problem of estimating parameters or parameter compensation more or less equally, it being common to all of these approaches that they are not capable of ascertaining the exact transmission channel parameters.
In principle, it would also be possible to subject the stream of data received from the receiver to a fast Fourier transformation (FF) to assess the physical channel properties of a transmission channel, in order to then calculate from the data sequence obtained therefrom the physical channel properties of the transmission channel using a fitting method. A fast Fourier transformation does not, however, have a linear order but where there is a sampling sequence of n values, the order 0(n 1n(n)). To calculate the value sequence in the frequency range k×n×1n (n) elementary arithmetic operations are thus necessary, wherein the fitting method still has to be carried out following the fast Fourier transformation, and this requires a complex matrix inversion or a time consuming iterative method. On the basis of the non-linear order alone, a method of this type based on a fast Fourier transformation is not capable, at the highest possible sampling rate, of carrying out signal processing in real time without parallelisation measures. The degree of system complexity or calculation complexity is also extremely high.